Remove Consensus::Params parameter from ContextualCheckBlock

Summary:
Remove Consensus::Params parameter from ContextualCheckBlock
since it can be accessed from the config and is therefore redundant.

Solves T187

Test Plan: make check

Reviewers: jasonbcox, deadalnix, #bitcoin_abc

Reviewed By: jasonbcox, deadalnix, #bitcoin_abc

Subscribers: teamcity

Maniphest Tasks: T187

Differential Revision: https://reviews.bitcoinabc.org/D1028